The achievement and maintenance of inter-examiner consistency in the assessment of plaque and gingivitis during a multicentre study based in general dental practices.

This study set out to demonstrate that it was possible to train general dental practitioners (gdps) to achieve and maintain high levels of inter-examiner consistency in the use of simple periodontal indices over a 12-month period. The gdps were trained by one trainer in the use of the plaque index (PII) and a modified version of the gingival index (mGI) which assessed gingival bleeding only. All the gdps underwent intensive training and employed a technique, when assessing inter-examiner consistency in the use of the PII, such that the 1st examiner did not disturb in situ plaque from 50% of the circumference of a tooth. The problem of variation due to repeat probing, when assessing inter-examiner consistency for mGI, was overcome by one examiner lightly probing gingival margins and both examiners scoring the results. The problems relating to the multicentre nature of the study included: distance between the centres, the need for strict adherence to the study protocol, consistency in the use of forms and instruments, in the application of periodontal indices, and of inclusion and exclusion criteria. Techniques for overcoming these problems included: the planning and application of a coherent study design, which employed simple indices, a detailed protocol, the recruitment of very well-motivated gdps of similar age and experience as examiners, the recruitment of an experienced trainer who trained the gdps thoroughly and monitored their performance throughout the study, and repeat visits to the practices involved to explain the nature of the study to all their staff members. Initially, the gdps achieved inter-examiner kappa scores of 0.78-0.85 (mean 0.81) for PII and of 0.73-0.94 (mean 0.87) for mGI when assessing 168 sites for each variable. During the following 12 months, individual kappa scores, assessed every 3 months at 42 sites, ranged from 0.51-0.90 for PII and from 0.73-1.00 for mGI. Mean kappa for PII scores achieved by the five gdps fell during the study from 0.81 to 0.76, whereas that for mGI rose from 0.87 to 0.92. It is concluded that it is possible to train gdps to achieve high levels of inter-examiner consistency in the use of PII and mGI and for these high levels to be maintained during a 12-month multicentre study.